1. Field of the Invention
The present invention relates to diluting fuel-in-oil treating apparatuses of internal combustion engines and, more particularly, the present invention relates to a diluting fuel-in-oil treating apparatus of an internal combustion engine that can separate the fuel from the lubricating oil of the internal combustion engine while suppressing degradation of the oil, and that enables stable control of an air-fuel ratio at an air intake side.
2. Description of Related Art
Known conventional diluting fuel-in-oil treating apparatuses of internal combustion engines heat lubricating oil and separate the fuel from the lubricating oil by vaporization in order to suppress dilution of the lubricating oil which is caused by mixing of the fuel (e.g., Related Arts 1 and 2). Related Art 1 discloses such technology in which an oil heater is provided on an oil circuit of the internal combustion engine for heating the lubricating oil flowing in the oil circuit in order to separate the fuel by vaporization. Related Art 2 also discloses such technology in which a heater is provided at a bottom portion of an oil pan for heating the lubricating oil in the oil pan in order to separate the fuel by vaporization. In addition, other known conventional diluting fuel-in-oil treating apparatuses use a canister for temporarily adsorbing the vaporized fuel in blow-by gas and return the fuel to the air intake side based on an air-fuel ratio status (e.g., Related Art 3).    [Related Art 1] Japanese Laid-open Patent Publication No. 2004-190513    [Related Art 2] Japanese Laid-open Patent Publication No. 2004-340056    [Related Art 3] Japanese Laid-open Patent Publication No. 2005-315172
In the technologies disclosed in Related Arts 1 and 2, the fuel in the lubricating oil is vaporized using a heater. Since some fuels have a higher boiling point (e.g., 200° C. and so on) depending on the component thereof, heating lubricating oil up to approximately 130° C., which is the maximum temperature at normal use conditions, leaves equal to or more than 30% of the fuel component in the lubricating oil unvaporized. On the other hand, although heating lubricating oil up to approximately 200° C. allows substantially all the fuel in the lubricating oil to vaporize, degradation of the oil is accelerated. In addition, since rapid vaporization of the fuel causes a large amount of the fuel component to be reduced to blow-by gas, stable control of an air-fuel ratio is difficult to achieve at the air intake side. Particularly, the above-described problem is conspicuous with the technology disclosed in Related Art 1 since the heater is used to heat a relatively large amount of the lubricating oil flowing in the oil path that connects the oil pan to a lubricated part in the engine or in a bypass path provided in the oil path. In addition, the above-described problem is extremely conspicuous with the technology disclosed in Related Art 2 since all the oil in the oil pan is heated.
The technology disclosed in Related Art 3 uses a canister for adsorbing the vaporized fuel. The fuel immediately after separation may include both gas and liquid components depending on the temperature thereof. When this happens, the canister cannot adsorb the both components directly.